1. Many students             (询问建议)about learning vocabulary/

2. I                    (喜欢看) English films and            (听) real English songs .

3. -Did you                (过得快乐) last Sunday?

    -Yes,I did. I went to Beijing with my parent.

4. Boys and girls ,who knows                       (这个单词的意思)?

5. Before you start to talk to the foreign teacher,                          (深呼吸一下)

关于X线在物质中衰减的叙述，正确的是

A．X线衰减与X线波长无关

B．X线衰减与透过物质有关

C．线性衰减系数是以长度为单位的衰减

D．质量吸收系数是以质量厚度为单位的衰减

E．总衰减系数是各种衰减系数的总和